In known transponders, the analogue circuit further includes a clock extractor, of the low level or high level type.
When the extractor is of the low level type, the threshold value is constant. It is chosen to be sufficiently low so that the connection between the reader and transponder can occur even when transmission conditions are difficult. It must, however, be sufficiently high, as described in European Patent document No. 0732662, so that the damping time, necessary to reach the threshold value, is not too long when transmission conditions are good. This results in a compromise, which means that the pause time between two bits must be at least equal to ten periods of the sinusoidal signal.